Toxicity and Genotoxicity of five pyrolytic Bio-Oils produced from Wood, measured as Root Growth Inhibition and DNA Double-Strand Breaks in Allium cepa
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- Institutt for biologi 
Pyrolytic bio-oil is considered as a potential renewable energy resource that might replace fossil fuels in the future. Chemically, bio-oils are highly complex mixtures consisting of several hundred different compounds, formed during anaerobic thermal degradation of biomass. Several of the compounds are known to exert both toxic and genotoxic effects on living organisms. Genotoxic compounds include polycyclic aromatic hydrocarbons (PAHs), furan and catechol, while various acids, alcohols, aldehydes, ketones and phenols are associated with the toxic properties. So far, only a handful of previous studies have assessed the toxicological effects of bio-oils in living organisms, and contradictory results point of the need to perform more studies to elucidate the harmfulness of bio-oils.The aim of this master s project was thus to evaluate the toxic properties and the genotoxic potential of five bio-oils made from different feedstock species of wood (beech, pine, poplar, spruce, unspecified wood). Toxicity and genotoxicity were respectively measured as root growth inhibition and DNA double-strand breaks (DSBs), in the in vivo Allium cepa test system. The hypotheses were: 1. Small differences in chemical composition or concentration of bio-oils may cause highly different toxicological responses in A. cepa, 2. It might be possible to identify differences in chemical composition influencing the toxicological effect of bio-oils by comparing the results with provided chemical data. The results for toxicity showed that the five bio-oils caused a significant reduction in onion root growth with increasing concentrations. The toxic effect varied between the different bio-oils, and was ranked in the following order, according to the obtained EC50-values: Pine > Beech > Wood > Poplar > Spruce. The obtained results for measurement of DNA DSBs indicated that bio-oils produced from fast pyrolysis of wood can cause severe DNA damage at concentrations of about 0.0004 ml bio-oil/ml solution and higher. The different feedstock species of wood applied in the pyrolysis process, may also affect the genotoxic potential of the bio-oils. The provided chemical data did not explain the observed toxic or genotoxic effect very well, but differences in specific chemical composition were observed, which might have caused the difference in toxicological response. Considering that further upgrade of bio-oils is needed to obtain applicable bio-oils, the toxicological effects of the finished upgraded products is likely to be altered compared to the effects seen for the crude bio-oils. Further studies should thus focus on the upgraded bio-oil products, as these are most likely to be of environmental concern in the future.